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RE: Double Interpolation of a String

by davorg (Chancellor)
on Jun 22, 2000 at 14:30 UTC ( [id://19415]=note: print w/replies, xml ) Need Help??

in reply to Double Interpolation of a String

For doing stuff with these kinds of substitutions, I always use code like this:

use strict; my %trans = (color => 'red', fruit => 'apple', name => 'chromatic'); my $string = 'Hi, my name is $name. Please hand me a $color $fruit.'; $string =~ s/\$(\w+)/$trans{$1}/eg; print $string;


European Perl Conference - Sept 22/24 2000

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Infinite Recursion of a String
by tadman (Prior) on Feb 07, 2001 at 00:30 UTC
    With inspiration from davorg's above example, taking it a step further (and a step further (and a step further (...))):
    #!/usr/bin/perl -w use strict; my %trans = ( '$name' => 'Frank', '$color' => 'Cherry Red', '$time' => sprintf ("%d:%02d:%02d", (localtime(time))[2,1,0]), '$date' => sprintf ("%04d-%02d-%02d", (localtime(time))[5] + 1900, (localtime(time))[4] + 1, (localtime(time))[3]), '$dstr' => '$time on $date', ); my ($trans_rx) = join ('|', sort { length($b) - length($a) } sort map { quotemeta ($_) } keys %trans); my ($string) = 'I\'m $name and I prefer $color objects, at least +on $dstr'; while ($string =~ s!($trans_rx)!$trans{$1}!o) { } print "$string\n";
    For output like:
    I'm Frank and I prefer Cherry Red objects, at least on 15:33:43 o +n 2001-02-06
    This version doesn't replace stray references to things like $1.95 with nothing, but it might get caught in a loop if you specify two entries which convert to eachother recursively such that "$a -> $b" and "$b -> $a".
      It might be useful to protect against infinite recursion as well:
      my $max_recurs = 10; $max_recurs-- while $string =~ ... && $max_recurs; warn "Too many recursive substitutions on '$string'" if !$max_recurs && $^W;

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